Developers should be able to specify grid column sort config property which is different from column field property.For instance, when listing products, my view model may have CategoryName property mapped from EF entity navigation property Category.Name using AutoMapper, while my sorting will use "Category.Name" on the server side.Example config could be like: 
columns[{title:"Category",field:"CategoryName",sort:"Category.Name"}]

This will allow me to flatten my view model without loosing sorting functionality.